This invention relates to an improvement in push-pull power amplifier circuitry.
Conventionally, a single-ended push-pull (abbreviated SEPP hereinafter) power circuit, as shown in FIG. 1a, is frequently used as an audio power amplifier circuit. In particular, an SEPP power amplifier circuit which is biased to pass a fixed, small amount of idling current for effective power efficiency is used.
However, in the case of the SEPP power amplifier circuit of FIG. 1a, transistor 1 of the driver stage and transistor 3 of the output stage switch alternately with transistor 2 of the driver stage and transistor 4 of the output stage when a positive or negative half cycle input signal is impressed due to the voltage drops produced at resistors 7 and 8. These resistors are connected between the respective emitters of transistors 3 and 4 of the output stages and the common output terminal C. In particular, the emitter currents IQ.sub.3 and IQ.sub.4 of output transistors 3 and 4 are alternately cut off as shown in FIG. 1b. As a consequence, switching distortion is produced at load 9 caused by a carrier storage effect, etc. of the transistors, resulting in a shortcoming in that the distortion factor of the power amplifier circuitry deteriorates.